1. Field of the Invention
This invention relates to the field of water purification, and in particular to an electrical purification apparatus and method which may be employed in place of chlorine water purification.
2. Description of the Prior Art
The use of copper ions as an algicide, and the use of silver ions as a bactericide, are both known in the art. Various procedures are known in which such ions are caused to be distributed in water to be purified where the ions combine with, and eliminate, algae and bacteria, respectively. Although the effect of these ions in reducing concentrations of various organisms is known, the problem remains as to how the ions are most efficiently generated and distributed.
In order to purify water, it is necessary to provide an adequate concentration of the silver or copper ions. One possibility is to employ immersed copper or silver electrodes connected to a source of electric potential. Unfortunately, the result of simply connecting a potential to electrode plates is that the ions migrate to the cathode, and are there deposited. Plating formed in this manner degrades the ability of the apparatus to produce ions because the plating tends to insulate the cathode from the electric current.
Methods and apparatus for purifying water using electrical techniques are shown in U.S. Pat. Nos. 4,263,114-Shindell, 3,752,747-Treharne et al, 4,098,660-Eibl et al and 3,936,364-Middle.
The Shindell patent attempts to avoid any direct electrical connection to the electrodes. Instead, a quantity of silver and a quantity of copper are joined along a junction. The joined body is immersed in the water, which is lightly salted, and an electric field, not directly connected to the electrodes, is placed across the device.
Of the remaining patents cited, Treharne et al teaches use of silver electrodes to produce ions toxic to algae. Eibl et al each such a device also including a semi-permeable membrane. The patent to Middle discloses a multi-chamber device including a module having silver electrodes and a module having zinc or steel electrodes.
In connection with preparation of drinking water, and with purifying water for swimming pools, saunas, air conditioning reservoirs, and the like, the most common form of water purification is treatment with chlorine, and filtering. Chlorine is effective to kill bacteria and algae. However, chlorine is also dangerous in concentration, and potentially irritating or unpleasant in any event. Chlorine has a strong odor, corrodes exposed surfaces, and may aggravate respiratory disorders, skin conditions and eye irritation. Chlorine is also a temporary or repetitive treatment in that the chemical is deactivated by sun, rain, and changes in temperature. Inasmuch as the level of active chlorine varies due to the particular conditions, the swimming pool or other water reservoir must be frequently tested for adequate chlorine levels. Although effective to eliminate algae and bacteria, chlorine has substantial adverse qualities as well.
The present system employs electrodes formed from a particular alloy of copper, silver and nickel. The electrodes are immersed in a cell through which water is pumped. By applying an electric field at a relatively low voltage, copper and silver ions are simultaneously released from the electrodes into the water flowing through the purification cell. Simultaneous release of ions produces a cooperative effect in which relatively low ion concentrations achieve the desired result. Plating of the cathode is avoided by periodically reversing the polarity of the voltage applied to the two identical electrodes. Accordingly, copper and silver ions in sufficient concentrations to be toxic to algae and bacteria are released indefinitely into the water without the requirement of regular additional service. A filter is recommended in addition to the invention, in order to remove particulate matter and the like. Nevertheless, the electronically controlled release of ions from the electrodes produces water pure enough for human consumption without the inconvenience, objectionable odor, taste and chemical effects of chlorine or other oxidizing agents.